Inclined Wood Joists

[NewbieStruct]

I am designing my first wood roof for a project. We have wood roof joists supported at one end by a ridge beam and bearing on a wood stud wall on the other end. The architect has roof sloped (slope is 15.6 in 12) at a particular location. Is there something that I need to be concerned about in terms of bearing on the wood top plate (in terms of shear stresses) on top of the wood studs.

 

[BAretired]

Yes, you should not exceed the allowable shear value for the top plate.

BA

 

[woodman88]

Your dead load along the slope (15.6/12) increases to 1.64 horizontally.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[hokie66]

Those are rafters, not joists. As this is your first wood roof, this is a good time to learn the terminology.

 

[a2mfk]

I have rarely needed anything other than a double top plate in wood framing...

When you get down to your lateral design, make sure to detail diaphragm shear transfer from the roof sheathing into the wall. Usually done with blocking between the rafters. Another common error is to not consider both uplift and out-of-plane forces on the connection between the top plate of the wall and the roof rafter.

One of the best things taught to me early on about structural engineering- the devil is in the details. And don't leave connections to the last minute, this is where a lot of mistakes are made and these are the weak links in any structure.

 

[NewbieStruct]

Thank you guys for all the information. I will incorporate your comments in designing and detailing the wood rafters.